Vegetable and Field Crops 195 



Sclerotinia white-rot (Sderotinia Uhertiana) occurs to some 

 extent (see lettuce). Root-knot (nematodes) and Southern 

 blight (Sclerotiwn rolfsii) are also common. 



GOLDENSEAL (Hydrastis) 



Botrytis-blight. This is the most common and widely 

 distrihutetl disease of this plant. Ten to 20 per cent of the 

 tops are reported affected in New York, Michigan, and 

 Wisconsin. 



Blight (Alter naria sp.). — Spots o(;cur upon the leaves. 

 The disease seems to be identical with that of ginseng. 



HOP 



Powdery-mildew {Sphcerothcca humuli (DC.) Burr.). — 

 Powdery-mildew, while serious in many parts of Europe, 

 has been seen but rarely on the hop in America, and has 

 seldom been reported as seriously injurious. It is recognized 

 by the usual characters of the powdery-mildews. See grape. 

 If it should become troublesome, spraying with Bordeaux 

 mixture or ammoniacal copper carbonate must be prac- 

 ticed. 



Leaf-spot {Cylindrosporiu7n humuli E. & E.).- — Small, 

 rusty brown, angular leaf-spots largely limited by the veins 

 are present. They show most clearly upon the lower sides of 

 the leaves. Minute black acervuli are present. The disease 

 has been reported from several states, but has not been re- 

 garded as serious. 



HORSE-RADISH 



Leaf-blight {Septoria armor acice Sacc. and Ascochyta ar- 

 moracice FcL). — Ruin is occasionally brought to a crop by 

 these diseases. The leaves bear numerous circular spots, 

 blanched in the center and pale yellow at their borders. 

 Pycnidia are borne in the centers of the spots. Badly affected 

 leaves turn yellow and become filled with holes caused by the 

 dropping of the dead tissue of the spots. 



